1. Field of the Invention
The present invention relates to a microphone array system. In particular, the present invention relates to a system that performs various kinds of signal processing with respect to sound signals received at each microphone to provide various functions.
2. Description of the Related Art
Hereinafter, a sound signal processing technique that utilizes a conventional technique will be described.
In the case where a plurality of sound sources of a desired signal and noise are present in a sound field, high quality enhancement of the desired sound, detection of the direction of the desired sound and noise suppression are important issues to be addressed for sound signal processing. Possible applications that utilize sound signal processing are in a wide range, such as animation and sound recording, systems for voice memo, hand-free telephones, teleconference systems, guest-reception systems or the like. In order to realize processing for enhancing a desired signal, suppressing noise and detecting the direction of the sound source, various sound signal processing techniques are under development.
Conventionally, microphones suitable for a particular application are used to obtain input sound signals for use in the processing for enhancing a desired signal, suppressing noise and detecting the direction of the sound source. For a compact video camera, a stereo microphone of MS (mid-side) system is widely used. In recent years, a unidirectional microphone is used in a personal computer that utilizes sound input in application software such as a voice memo, so that a suitable and articulate input sound signal can be obtained. Although these microphone are suitably used in view of the use and the cost, they are intended for a single use so that the directivity or the use is predetermined. Moreover, the processing of the sound signals received at the microphones is limited to the sound signal processing required by the application.
In an apparatus such as a conventional video camera or sound-inputtable personal computer that requires microphones suitable to each application and implements only sound signal processing required by the application that currently runs, the microphone and the sound signal processing function are each intended for a single function. However, for the apparatus designed to have a large number of functions, more flexible directionally received sound processing, sound source direction detecting processing and noise suppressing processing are desirable, and a function that has not conventionally required may be required in an application. In this case, since the configuration of the apparatus using the conventional microphone with a single function cannot meet this need, it is necessary to replace the microphone by a microphone suitable to the required function and also to replace the sound signal processing part for received sound signals by another one having the required function.
As the utilization system is varied, combining a plurality of kinds of sound signal processing such as directionally received sound processing, sound source direction detecting processing, noise suppressing processing and the like may be needed. In this case, it is necessary to prepare a plurality of microphones, each of which has a single function, and to perform sound signal processing for each individual microphone, and then perform sound signal processing of the combined results from the plurality of microphones. Thus, this conventional system requires a large number of microphones, so that it results in a large-scale apparatus. Furthermore, it may be difficult to physically arrange the required number of microphones to perform a plurality of kinds of sound signal processing in the necessary directions.